A conventional multi-layered semiconductor device may include a contact hole, which electrically couples a wiring pattern, formed in an upper layer, to an electrode, formed in a lower layer. A barrier metal may be formed on an inside surface of the contact hole, and is alloyed with the electrode in a RTN (Rapid Thermal Nitridaition) process. After the RTN process, a contact material is filled in the contact hole. However, according to the conventional semiconductor device, voids may be formed between the contact material and the electrode. As a result, electrical connection between the wiring pattern and the electrode would be deteriorated.